Trouble with 7950's drawing way too much power.

[LAC_STS]

I dunno if I should put this in the PSU section of the GPU section.


I have a mining rig. It is:

ASRock 970 EXE4
8GB DDR3
Athlon II
5x 7950's
Silverstone gold single rail 1200W PSU (my original plan was to run 4 cards off of this 1200W PSU and the 5th card off of a single rail PC P&C gold 500W PSU.) Right now though I have to run dual 1200W PSU's.)


So this is whats up. I have read of many many people who run 3 7950 rigs off of 800W PSUs. The 7950's max TDW is 200W.


I have a kill a watt hooked up. (Its plugged into the surge protector with the PSU plugged into that.) It reads 1150 W with the system and 3 7950s hooked up to it.

I have another 1200W PSU running the other 2 cards. Like I said above I want to run 4 off of one of the 1200W PSUs and the 5th card off of a 500W PSU.



I cannot run 1 card off of a 500W PSU. I cannot run 4 cards off of the 1200W PSU.


Why are these cards using so much power? Could it be the way I have the dual PSUs setup? I have it set up just by shorting the green ATX wire to ground as described HERE.




Anyone have any ideas? I would greatly appreciate any help/suggestions.

 

[Bobnova]

That guide is good for running a PSU on a bench. To correctly run two PSUs in a single system you need to connect the two green wires (one from each PSU) together so that the PSUs turn on at the same time.
Additionally if the second PSU does not have DC-DC or independent regulation for the secondaries it will not appreciate the 12V-only load of GPUs.

 

[Boulard83]

at stock, 7950 can pull over 200w while benching and if you OC the cards, thy can break the 300w barrier EZ. HD79xx are way less efficient than Nvidia GTX680/70. I can hardly break 250w on my 670 at 1200mhz and higher.

4 7950 with mild OC will pull over 1000w alone while benching.

http://www.techpowerup.com/reviews/HIS/HD_7950_X2_Boost/26.html

 

[nookuwn]

your numbers don't seem right, for comparison here are my numbers running 2x HD7950.

Pulling ~530W at the wall
Asus M5A990FX Pro r2.0
Athlon II X4
2x2GB
Corsair 750TX
2x XFX DD HD7950
I'm getting 530kh/s each card at intensity 18 for litecoin. With these numbers I could even add another card, but there's no PCI-E power connector left.

 

[LAC_STS]

So I have two of these rigs with 5 7950's.

I hooked another one up yesterday. I tried with both a 1200W Silverstone PSU and I tried with a 1200W Cooler Master PSU.


Same results. The cooler master actually draw more. The Silverstone draws 1150 W and the Cooler Master draws 1200-1250 W.

These are just running 3 7950's and the system.

The wierd thing is that my second PSU only draws 450W running 2 7950's and a case fan.

 

[LAC_STS]

So to summerize I have two 5X 7950 rigs.

Besides the PSU's the specs are:

ASRock 970 EXE4 (other is a 990 EXE4)
8GB DDR3
Athlon II dual core
no HDD just USB stick running BAMT (Linux distro just for mining)

I have hooked the PSUs up correctly now by wiring them together instead of just the paperclip turn on second PSU thing.

 

[Knufire]

Maybe start removing cards and see how much power usage drops?

 

[xsuperbgx]

do you have the 7950s overclocked? i would put them at stock speed and try to undervolt. that might get you low enough to run them all off of one psu. with the increasing difficulty, efficiency is ever more important.

 

[ShrimpBrime]

Maybe something like this 2000w would do the job?? http://www.epowertec.com/ep-2000p10-t3.html

Newegg says out of stock though

 

[peanutbudder]

Did you say five 7950's!!! I want pictures of that beast!

I think my apartment would catch fire with that kind of power draw. I have an overclocked 2500k and two 560 ti's at 920mhz and my killawatt measures 549 watts and the lights flicker in the living room. I have tripped the breaker several times if I have all three monitors running with the pc on and somebody (wife) turns on the light... click- no power.

 

[EarthDog]

I'd be floored if a 7950, not modified, would break 300w use overclocked as far as it could go. Its a 205w card and has a 20% power limit on it so its not going to break 250w really.

A 1200w psu should run 5 at stock speeds no problems.

 

[ShrimpBrime]

I'd be floored if a 7950, not modified, would break 300w use overclocked as far as it could go. Its a 205w card and has a 20% power limit on it so its not going to break 250w really.

A 1200w psu should run 5 at stock speeds no problems.

It would be close, but doable. I agree with earthdog here.

Ran a 4850x2 and two more 4850 single slotters for quad fire and that ran on an Antec True power 550 watter..... and the PSU did eventually die.... The system was also running a 140w 9950BE at the time as well. Never a sign, just died.

But really, to have a 2000w would be killer. I often drooled over the EPower 2000 because of running TECs and multi card set ups. But I've found the 850w and 1000w to usually be more than enough for at least Tri fire with just about any Gpu setup out there.

 

[LAC_STS]

Sorry for not posting back for so long. I am not getting notified of new posts by email anymore I guess.

I had to move my rigs into a small extra bedroom I have because they were generating so much heat. And with the hot FLA summer starting up I have to figure some stuff out with the heat. I have two vents in that room and Im gonna run some duct from each vent down to the intake on the cards. Then I should be able to shut the bedroom door and the cards be ok. Right now if I shut the door all the way they get too hot. And by the way anyone wanting to order these cards they are LOUD. Like leaf blower loud.

I have dual PSUs. I did have the second one just jumped to turn on but now I have the PSUs correctly wired together.

I used this guide.
http://www.burningissues.net/how_to/power/adaptor.htm

The second PSU only draws 450-500W running 2 7950's. So that seems about right.

Someone on the BTC forum seems to think that running dual PSUs usually gives "bad juju". His words not mine. He suggested to just try to run 4 cards off of one 1200W PSU and see what happens.


If it runs 4 off of one 1200W PSU then something must be going on with the dual PSU setup. Because right now the main 1200W PSU is maxed out just running three cards.

I have tried swapping around different PSUs. I tried a Cooler Master 1200W gold, Silverstone 1200W gold, and an older Silverstone ZEUS 1200W.

They all run 1150-1250W with three cards hooked up to them.


My windows 7/8, X58, single PSU rig with 3 7950's only pulls about 950W.

 

[ShrimpBrime]

Sorry for not posting back for so long. I am not getting notified of new posts by email anymore I guess.

I had to move my rigs into a small extra bedroom I have because they were generating so much heat. And with the hot FLA summer starting up I have to figure some stuff out with the heat. I have two vents in that room and Im gonna run some duct from each vent down to the intake on the cards. Then I should be able to shut the bedroom door and the cards be ok. Right now if I shut the door all the way they get too hot. And by the way anyone wanting to order these cards they are LOUD. Like leaf blower loud.




I have dual PSUs. I did have the second one just jumped to turn on but now I have the PSUs correctly wired together.

I used this guide.
http://www.burningissues.net/how_to/power/adaptor.htm

The second PSU only draws 450-500W running 2 7950's. So that seems about right.

Someone on the BTC forum seems to think that running dual PSUs usually gives "bad juju". His words not mine. He suggested to just try to run 4 cards off of one 1200W PSU and see what happens.


If it runs 4 off of one 1200W PSU then something must be going on with the dual PSU setup. Because right now the main 1200W PSU is maxed out just running three cards.

I have tried swapping around different PSUs. I tried a Cooler Master 1200W gold, Silverstone 1200W gold, and an older Silverstone ZEUS 1200W.

They all run 1150-1250W with three cards hooked up to them.


My windows 7/8, X58, single PSU rig with 3 7950's only pulls about 950W.

Very nice. Looks awesome to say the least.

Bad juju is for the superstitious people. Heck run three if you need to.

If your PSU's run warm, get more air flow through them. It'll help keep from baking them if your running for extended periods of time.

Glad you got it working though!

Are we going to see a few benchmarks??

 

[LAC_STS]

Very nice. Looks awesome to say the least.

Bad juju is for the superstitious people. Heck run three if you need to.

If your PSU's run warm, get more air flow through them. It'll help keep from baking them if your running for extended periods of time.

Glad you got it working though!

Are we going to see a few benchmarks??

What kind of benchmarks are you talking about? Unless its KH/s I will not have any.



These rigs are setup for mining only. They are running BAMT which is a custom Linux distro that is made only for mining. Besides initial setup the rigs are run headless.

I only have the monitors hooked up there in case they crash I can get them back up and running faster using a monitor vs SSH.


BAMT is really the only way to go with these mining rigs. I couldnt imagine having to deal with 3 windows installations mining 24/7.


My third rig is Windows based because its my main computer. Its an X58 and with three 7950's it only draws 900-950 W.


And thats a:

i7 965 EXE
EVGA FTW3 X58 (Did have the Rampage II but I Fed it up doing something stupid)
12GB DDR3 (6 x 2 GB)
Intel 520 240 GB SSD
2 Velociraptor 320 GB in RAID 0 (used to be boot drives until I got the SSD)
2 x Seagate 1.5 TB 7200 RPM
1200W Cooler Master Gold PSU
Thermaltake Level 10 Snow Edition
3 x 7950's

And all this only uses 900W







I have read of people having really good power savings with Gigabyte 7950's by flashing to the F43 (or something like that F something) BIOS.

Anyone know of a similar Sapphire BIOS? I looked on Tech Crunch and they dont specifically describe which BIOS are for which cards. I know Sapphire has tons of different 79xx models so maybe that is why.

 

[LAC_STS]

For some reason I have been thinking that I have had these cards running at 1.15V.

I just noticed that both rigs are running 1.25V.


Now Im probably wrong about this but isnt the difference between running at 1.15V and 1.25V something like 50ish W per card?


Gonna push them down to 1.15V and see what the draw is.

 

[EarthDog]

Depends on the cards... I have seen 7950's @ 1.25v default, so be careful, they might not like 1.15v at stock speeds, and especially not overclocked.

 

[LAC_STS]

Depends on the cards... I have seen 7950's @ 1.25v default, so be careful, they might not like 1.15v at stock speeds, and especially not overclocked.

I have my Windows 7/8 Rig at 1.15V. On the Sapphire TRIX utility I think they default at 1.068 Im not sure but I know my Windows rig is at 1.5 and its stable. Same clocks.


By the way I am running all of these cards (both BAMT and Windows rigs) at 1075/1500. Stock is 925/1250

 

[LAC_STS]

Does anyone have any idea about when I switched the main PSU to 4 cards?


Whether running 3 cards or 4 cards it is still reading about the same W. I know my kill a watt is not broke because I tested it on a hair dryer and on some 100W lightbulbs.

 

[xsuperbgx]

I think you should be able to run those clocks with stock volts or even lower than stock. A combination of lower voltages and underclock may get you all on one power supply.

I have 3x7950 and one 5770 on a 1000w psu. I will plug it into my killawatt this weekend.